Kurobe Gorge train stops

How long does the Kurobe Gorge train stop at each of the stations? Is there enough time to walk around and see the sights of the area? Is the stop at the end (Keyakidaira) enough time or should a reservation be made on a later train to return to Unazuki?

As in most cases of short train rides in Japan,
a Kurobe Gorge Railway ticket does not allow you to get outside ticket gates.
When you plan to do sightseeing around a station,
you should purchase separate tickets to travel to and from the station.
http://www.kurotetu.co.jp/en/fare/index.html

The train only stop enough time to do its thing. If it arrives early. You may have a few minutes.

You need to decide which stopd you want and how much time you need. And book your tickets accordingly.

Thank you omotenashi and hakata14 for your answers. From what I read on how to make reservations, if I want to get off anywhere between Unazuki and Keyakidaira, I would have to buy my tickets on that day. If I want to make reservations online ahead of time, only straight through tickets can be bought. So I can take a later train from Keyakidaira back to Unazuki. Is this correct? Also, is there a picnic area around the Keyakidaira station where we can eat a bento lunch?
Again, thank you very much for all your help.

Yes, it is a good idea to bring along a bento box for lunch, because there is very little choice of restaurants at Keyakidaira.